The invention relates to a packet-switched communication network. More particularly, the invention relates to a data carrier detector for such a network.
Packet-switched communication networks evolved from the need to conserve data communication resources. Since data is sent in discrete packets, rather than as a continuous transmission, gaps in communication on one connection may be efficiently utilized by providing packets from other connections to fill those gaps. An example of a radio communication system, which utilizes packet data communications to communicate information between a sending station and a receiving station, includes a Mobitex™ system.
A Mobitex system is a multi-user system formed of a Mobitex network and a plurality of mobile radio modems. Information to be communicated to a mobile radio modem is formatted into frames of data, each frame of data forming a packet which may be transmitted to the mobile radio modem through a radio communication channel. Sequences of frames are transmitted to the mobile radio modem to effectuate the communication of significant amounts of information to the mobile radio modem. When the mobile radio modem receives a message frame, the modem transmits, back to the Mobitex network, an acknowledgment signal, acknowledging reception of the message frame.
However, because a radio communication channel is not an ideal channel, the message frames transmitted upon such channels are susceptible to signal quality degradation. Such signal quality degradation may occur, for example, due to interference or noise introduced upon the signal channel, excessive separation distance between the Mobitex network and the mobile modem, or other communication problems. If the signal quality degradation is significant, a message frame transmitted by the Mobitex network may not even be detected by the mobile radio modem.